The Harvard-educated University of Alabama biology professor accused of slaying three of her colleagues and wounding three others shot dead her teen brother in a Boston suburb in 1986, authorities said yesterday.

But records of what happened to Amy Bishop’s 18- year-old sibling have disappeared — fueling suspicion that the true circumstances of the shooting, which was ruled an accident, were covered up.

“I don’t want to use the word ‘cover-up,’ but this does not look good,” Braintree, Mass., Police Chief Paul Frazier admitted yesterday at an explosive press conference, as reported by The Boston Globe.

Bishop, 42, shot her brother, Seth, in the abdomen while unloading a 12-gauge shotgun, reports said at the time. The gunplay was ruled an accident, and Bishop was released into her mother’s custody.

When she spoke to investigators 11 days later, she told them she could only remember hearing her mother scream. She also reportedly said she was unaware that she had shot her brother.

But Frazier painted a different picture in which Bishop shot at her brother three times in the heat of an argument. She then fled with the shotgun, unsuccessfully tried to carjack a passing motorist and was arrested at gunpoint, he claimed.

Frazier based his bombshell allegations on his own recollections and those of one of the arresting cops.